Why has the Catholic Church never recognised St Patrick as an “official ” Saint?

There are cases whereby some saints were done so popular demand or cultural acceptance, such as St. Christopher (depicted carrying a child Christ across a river), that were removed – so to speak – during Pope Benedict’s papacy due to lack of evidence etc.

These saints were never “officialy” recognized per say. That's why the Church goes through a vigorous investigation of claims and evidence prior to beatification or canonization.